A Holden Cruze, equipped with an F18 engine made it's way into one of our members workshops this week for a 500km inspection after a recent head replacement.
As soon as the vehicle pulled into the workshop, it was apparent that something was not right as there was a distinct smell of burning oil.
Upon popping the bonnet, it was evident that thre was an oil leak coming from the front of the engine.
The oil was cleaned and the engine ran for some time to try and identify the cause however there was nothing blatantly obvious, other than a film of oil around one of the rocker cover bolts. This was degreased and the engine rechecked again.
Same thing! A film of oil around that same rocker cover bolt.
At first, it was suspected that there was a crack in the rocker cover but this was not the case.
Upon removal of the rocker cover, it was evident that the oil was in fact leaking through the thread of for the rocker cover retaining bolt in question.
What was causing this?
After making contact with the supplier of the cylinder head, It was determined that there was an issue with the programming of the CNC machine and that the rocker cover bolt holes were being drilled too deep and making contact with an oil gallery in the head.
The fix in this case was to fit an m6x5mm grub screw into the hole with hydraulic sealant and fit a shorter rocker cover bolt.
It just goes to show there are alot of strange scenarios that can occur during repairs that are beyond our control. In this case, being vigilant has paid off!
Thanks to Joshua Forge of Forge Performance for sending in this case study
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